How would i go about finding neighborhood demographics data for the neighborhoods I lived in during 1990 and 2000? I would prefer something more detailed than city data. I want to split the data down to the level of the few surrounding neighborhoods.
The closest to a "neighborhood" might be an area known as a census tract. You can look up the census tract IDs for the neighborhood you're interested in using the Reference maps found here: https://www.census.gov/geographies/reference-maps/2000/geo/2000-census-tract-maps.html for 2000 and here https://www.census.gov/geographies/reference-maps/1990/geo/1990-census-tract-maps.html for 1990.
Then look for historical data for those tracts from the 1990 Census and 2000 Census. https://www.census.gov/main/www/cen2000.html
Another option might be to contact your local State Census Data Center for help finding the correct data: https://www.census.gov/about/partners/sdc/member-network.html
In my experience, tracts are a very poor substitute for neighborhoods. I was recently tasked with comparing both tracts and ZCTAs to designated neighborhoods in St. Louis. The takeaway: Tracts are better than ZCTAs, but neither one is a good or even "close-enough" fit. Your mileage may vary of course.
(tracts green, neighborhoods red)
Also, I believe that in 1990, tracts did not have full coverage. AMC8's city might not even have tracts for 1990.
The U.S. was fully covered by tracts for the first time in 1990. (Technically, many of these were "block numbering areas" (BNAs), nominally not census tracts, but the BNA data are delivered exactly as tract data, so it's effectively full coverage.) There's also nationwide coverage of block groups and blocks in 1990, so identifying sets that match up with neighborhoods should be do-able. All of these data are freely available via IPUMS NHGIS.
Yes. 1980 was the last time it was incomplete